GCN Circular 6443
P.A. Price (IfA, Hawaii) and T. Minezaki (IoA, Tokyo) report on behalf of a larger collaboration: We observed the optical afterglow of GRB070518 with the MAGNUM telescope + MIPS dual-beam camera. Observations commenced 10.6 minutes after the trigger, with a mid-point time of 2007 May 18.614 UTC. Based on calibration using a single USNO star (optical image; as for GCN #6418) and single 2MASS star (NIR image), we find: R ~ 19.5 mag J ~ 18.8 mag This message may be cited.